Sheet-extracting device with a cassette for receiving a stack of sheets

ABSTRACT

The invention relates to a sheet-extracting device with a cassette for receiving a stack of sheets, and to a method of controlling the pressing force of the stack of sheets against the extracting device. The latter has extracting rollers (16) which are arranged on a floating shaft (34). For its part, the floating shaft (34) is centrally connected in a rotationally fixed manner to a drive shaft (18) passing through it. The drive shaft (18) is mounted, by one end (20), in a frame-mounted bearing (21) and, by its other end (62), in a displaceable bearing (64). Acting on the bearing (64) is a force sensor (70, 74, 76) which is intended for determining the pressing force of the stack of sheets (12) against the extracting rollers (16). The pressing force is controlled such that it always moves within a narrow middle range between a minimum and a maximum possible value.

BACKGROUND OF THE INVENTION

The invention relates to a sheet-extracting device with a cassette forreceiving a stack of sheets, and to a method of controlling the pressingforce of the stack of sheets against the sheet-extracting device.

Cassettes of this type are used in sheet-extracting devices, inparticular in automatic banknote dispensers. The pack of banknoteslocated in the cassette is pressed by a pressing element against an endwall of the cassette, which is designed such that the respectivelyforwardmost banknote is in contact with extracting elements reachingthrough the end wall. These extracting elements are normally extractingrollers, but may also be extracting fingers or the like.

It is already known to press the pack of banknotes by a sprung pressingplate against the extracting elements, the pressing plate triggering thecontrol of a pressing slide by means of a displacement sensor. In thiscase, it is scarcely possible to ensure a constant pressing force, sincethe friction of the banknotes in the cassette changes with the number ofbanknotes in the pack and according to their condition (bends, folds andthe like).

In the case of a known sheet-extracting device of the type mentioned asdisclosed in DE 34 34 780 C2, the pack of banknotes is pressed againstthe extracting rollers by means of a pressing plate, which is displacedin the cassette by a motor. In that case, the pressing force of theextracting rollers against the forwardmost banknote is measured and usedfor controlling the drive motor. For that purpose, the spindle of theextracting rollers is mounted displaceably in the pressing direction onone side, it being supported directly against a force sensor. Thebearing force measured by the force sensor is directly proportional tothe pressing force of the stack of sheets on the extracting rollers.

However, the oblique position of the extracting shaft with respect tothe stack of sheets, said position being caused by the yielding of thespindle on one side, creates the risk of extraction errors and of thebanknotes skewing. This problem is heightened in that, in particular,stacks of banknotes are not of equal thickness over the entire surfaceof the stack. All the distortions, packing deformations, security-threadthickenings and gravure embossing on the note bundles result, in thecase of large stacks, in changes in the stack thickness over the surfaceof the stack and thus also in unequal pressing forces on the extractingrollers. Compensation of these differences in thickness especially inthe case of large filling quantities of, for example, more than onethousand banknotes in the cassette by virtue of a relatively highpressing force is not possible, or is possible only to an unsatisfactoryextent. However, the extracting system as a whole only operates withoutdisruption when the banknotes are extracted from the cassette in asstraight and uniform a manner as possible.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a sheet-extractingdevice with a cassette of the type mentioned at the beginning whichensures a uniform pressing force by simple means and in the case ofwhich satisfactory extraction of the individual sheets from the stack isensured even when the surface of the stack is not fully planar, and alsoto give a method by which the pressing force can be controlled.

This object is achieved by the present invention.

The invention is based on the finding that, in the case of a rotatingextracting shaft with at least two extracting rollers, the only abutmentof which is located between the extracting rollers and at the point ofintroduction of the torque, the entire pressing force acts on saidabutment and can thus be measured there. This force is passed on to thedrive shaft and can then also be measured in the bearings thereof. Sincethe ratio by which the pressing force is distributed to the bearingsalways remains the same, it is sufficient to measure the force at oneend of the drive shaft. Guiding the floating shaft between legs of aguide fork which are directed perpendicularly with respect to the sheetplane ensures that it is only forces which are directed perpendicularlyonto the surface of the forward-most sheet which take effect and areinvolved in the measurement. The floating shaft, which can be pivotedfreely about its floating axis passing through the abutment, is not onlyadapted to unevenesses in the end face of the stack, but also ensuresequal distribution of the extraction forces even in the case of unequalcoefficients of friction on the extracting rollers.

Such an arrangement also tolerates the skewed position of a drive shaftwhich yields on one side, with the result that the problems arising inthe prior art are eliminated. According to a development of theinvention, the torque is introduced into the drive shaft on the fixedlymounted side. It is then only the bearing reaction forces which have tobe absorbed. The other end of the drive shaft is mounted displaceablyperpendicularly with respect to the sheet plane. The force sensor actson said end.

The pressing force is determined by a spring which is coupled in africtionally locking manner to the displaceable shaft end. Thedislaceable pressing element pushes the stack of sheets against theextracting device and thus deflects the drive shaft. The spring is thussubjected to stressing and produces a reaction force which correspondsto the pressing force. The excursion displacement of the spring is thusa measure of the pressing force of the stack of sheets on the extractingdevice. A displacement sensor which detects the excursion displacementmay then be used as force sensor.

The cassette can be fitted on the extracting device by pushing it on. Inthis case, the displacement sensor is designed such that it can alsogive out information on whether a cassette is pushed on or not. Thedisplaceable shaft end is mounted in a displaceable bearing. This ismoved into a first displacement position by the spring when the cassettehas been removed. When the cassette is pushed onto the extractingdevice, it acts on the bearing and displaces it, counter to the springforces, into a second position. This is indicated by the displacementsensor to a control means, which then, for its part, activates thepressing device, as a result of which the stack of sheets in thecassette is pushed against the extracting device, whose shaft yields ashas been described and thereby increasingly subjects the spring tostressing until the displacement sensor signals an excursiondisplacement which corresponds to a predetermined pressing force. Thepressing device is consequently switched off. The control method will bedescribed further with reference to an exemplary embodiment.

According to a preferred embodiment, the displacement sensor comprises areflection light barrier, the surface normal of a reflector which isfitted on the displaceable bearing being oriented in the displacementdirection. In this arrangement, a mirror-surfaced planar reflector givesmeasuring results which can be reproduced particularly well.

The reflector is arranged at such a distance from the light barrier thatthe spot of light produced by the light transmitter is imaged with highdefinition on the light receiver and with approximately the magnitude ofthe light-sensitive surface area of the light receiver. The change indistance between light barrier and reflector associated with thedisplacement of the displaceable bearing causes, in the abovedescribedarrangement, a displacement-dependent change in the degree ofillumination of the light-sensitive surface area. This results in alinear change, which is directly proportional to the displacement, inthe output variable of the light receiver. The output variable serves tocontrol the pressing motor.

Further features and advantages of the invention may be gathered fromthe subclaims and the following description, which explains theinvention with reference to an exemplary embodiment and in conjunctionwith the associated drawings, in which:

FIG. 1 shows a schematic partial side view of a storage container forbanknotes and the basic elements of an extracting and separating device,

FIG. 2 shows a plan view of an axis-containing section through thefloating shaft with the drive shaft,

FIG. 3 shows a schematic representation of an arrangement comprisingpressing, force-measuring and control system, and

FIG. 4 the characteristic curve of the force-measuring system in FIG. 3.

FIG. 1 shows part of a separating module which is designated in generalterms by 10 and comprises a cuboidal frame into which a cassette 14which contains a stack of sheets 12 is pushed. Extracting rollers 16 ofan extracting device of the separating module 10 lie on the forwardmostsheet of the stack 12 contained in the cassette. The stack 12 isprestressed in the direction of the extracting rollers 16 by a pressingdevice 13 (FIG. 2) actuated by a pressing motor 46, with the result thatthe sheets of the stack 12 constantly butt against the extractingrollers 16 with a certain degree of prestressing. In a manner which willbe explained in more detail at a later point in the text, the extractingrollers 16 are arranged on a drive shaft 18, one end 20 of which ismounted rotatably in a frame-mounted bearing 21 and can be driven in thedirection of the arrow B.

The extracting rollers deliver that sheet 22 of the stack 12 which isbutting against them in each case, or else, if appropriate, a number ofsheets 22, 24 adhering to one another, in the direction of a nip betweentransporting rollers 26 and counteracting rollers 28 arranged on shafts30 and 32, respectively, parallel to the drive shaft 18 and capable ofbeing driven, in the same direction as the extracting rollers 16, in thedirection of the arrow B. The task of the transporting rollers 26 is todeliver upward through the nip the sheet 22 butting against them, whilethe counteracting rollers 28 are intended to prevent more than one sheetfrom passing through the nip between the transporting rollers 26 and thecounteracting rollers 28.

The extracting rollers 16 are arranged on a tubular floating shaft 34.Three extracting rollers 16 arranged at an axial spacing from oneanother are provided, the central extracting roller being locatedprecisely in the center between the two outer extracting rollers.

The floating shaft 34 is mounted on the drive shaft 18 by means of auniversal joint, which is designated in general terms by 48. Theuniversal joint comprises a bearing ball 50 which is connected fixedlyto the drive shaft 18 and has annular bearing surfaces 52. In thepresent example, two axis-parallel grooves 54 are made in the surface ofthe bearing ball 50, only one of these grooves being visible in FIG. 2.

Bearing surfaces 56 in the form of ball sockets are made in the floatingshaft 34 in the region of the central extracting roller 16, precisely inthe center between the two outer extracting rollers. Extending towardboth ends of the floating shaft 34 from the bearing surfaces 56 arebores 58, the diameter of which widens conically toward the free ends ofthe floating shaft 34, with the result that it is possible for thefloating shaft 34 to be pivoted to either side by the angle β/2 from itscentral position directed parallel to the axis 60 of the drive shaft 18.

In order to permit a torque transmission from the drive shaft 18 to thefloating shaft 34 while maintaining the capacity for pivoting of thesame, pegs (not shown) which engage into the grooves 54 in the bearingball 50 are provided in the region of the central extracting roller, onthe inside of the floating shaft 34. This also means that, despite thetorque transmission about the axis 60, a pivot movement of the floatingshaft 34 about an axis perpendicular with respect to the plane of thedrawing is possible.

Since, for equal distribution of the extraction forces, it is only apivot movement of the floating shaft 34 perpendicular with respect tothe plane of the sheet 22 to be extracted, i.e. perpendicular withrespect to the stack end face, which is desired, the floating shaft 34has, at its end which is on the left-hand side in FIG. 2, a guideextension 36 which engages between the two legs 38 of a guide fork 40(FIG. 1) which prevents the floating shaft 34 from tilting about an axisperpendicular to the stack end face and permits only a floating movementof the floating shaft 34 about an axis parallel to the stack end face.The guide fork 40 is fastened on a carrier 42 which is connected rigidlyto the frame of the separating module 10 and is indicated schematicallyin FIG. 1.

With the exception of the pressing motor 46, the arrangement which hasbeen described thus far is known from German Patent Specification DE 4124 566 C1.

The other end 62 of the drive shaft 18 is mounted in a displaceablebearing 64 which is designed as a sliding block and can slide smoothlyin a slot 66 in the frame wall 68. A tension spring 70 acts on thebearing 64, and the other end of said tension spring is coupled, via apeg 72, to the frame wall 68. The spring 70 is arranged such that itpulls the displaceable end 62 of the drive shaft 18 in the direction ofthe cassette 14.

Fitted on that side of the displaceable bearing 64 which is remote fromthe cassette is a planar, mirror-surfaced reflector 74 whose surfacenormal is oriented in the displacement direction of the bearing 64. Areflection light barrier 76 is arranged opposite the reflector 74, itscenter line 78 being located perpendicularly on the reflector 74.

A carry-along member 80 which projects into the push-in path of thecassette 14 is integrally formed on the bearing 64.

The mode of operation of the sheet-extracting device according to theinvention is explained hereinbelow with reference to FIG. 3, which showsa schematic representation of the pressing device 13, arranged in thecassette 14, with the pressing motor 46, of a control device 44, and ofthe measuring system which comprises the spring 70, the reflector 74 andthe reflection light barrier 76 and is intended for measuring thepressing force. Reference is also made to FIG. 4, which shows thedisplacement path/output voltage characteristic curve of theabovementioned measuring system.

The focal distance of the optical system of the light barrier 76 and thespacing d between said light barrier and the reflector 74 are selectedsuch that a spot of light produced by the light transmitter 90 is imagedwith high definition in the plane of the light receiver 92 and with amagnitude which corresponds essentially to the light-sensitive surfacearea of the light receiver 92.

With the cassette 14 removed from the extracting system, the reflector74 is spaced apart from the light barrier 76 by a distance d₁ whichcorresponds to an oblique position t of the drive shaft 18 (for reasonsof clarity, FIG. 2 represents only those positions of the axis 60 of thedrive shaft 18 which correspond to the various oblique positions t, u,v, w of said drive shaft 18). In this position, the light receiver 92outputs a voltage U₁. This voltage is stored in a control means 44 asminimum value.

When the cassette 14 is pushed onto the extracting system, the cassetteacts on the carry-along member 80, as a result of which the bearing 64,and with it the reflector 74, is displaced in the direction of the lightbarrier 76. In this position, the drive shaft assumes an obliqueposition u. The light-receiver voltage U rises to a value which lies inthe bottom third of the operating range 94 of the light barrier 76. Fromthe fact that the voltage U has assumed a value other than U₁, thecontrol means 44 concludes that the cassette 14 is then located in anoperating position from which sheets 22 can be extracted from the stack12.

With control of the control device 44, the pressing device 13 is thendisplaced in the direction of the extracting device until voltage U₃ atthe top end of the operating range 94 has been set. The reflector 74 isthen at a spacing d₃ from the light barrier 76 and the drive shaft hasan oblique position w. From the values U₁ and U₃, the control means 44calculates a mean operating value for the pressing force of the stack ofsheets 12 against the extracting rollers 16, which, with an obliqueposition v of the drive shaft 18, results in a spacing d₂ betweenreflector 74 and light barrier 76. A voltage UM corresponds to thisspacing.

By activating the pressing motor 46 in the backward direction, thecontrol device 44 then reduces the pressing force to a value whichcorresponds to a voltage U₂ and is slightly above U_(M). If sheets 22are then extracted from the cassette 14, the pressing force decreases.As soon as the output voltage of the light receiver drops below thevalue U_(M), the pressing force is increased again to a valuecorresponding to U₂. The difference between the values U₂ and U_(M)corresponds to a predetermined number, preferably 10, of sheets 22extracted from the stack 12.

The abovedescribed arrangement permits precise control of the pressingforce of the stack of sheets 12 against the extracting rollers 16 withequal distribution of the extracting torque to all the extractingrollers. In this arrangement, the thickness of the stack of sheets isinsignificant. The resolution of the measuring system for the pressingforce is further increased in that the deflection of the reflector isincreased by the length ratio of the lever arms, formed by the driveshaft 18, which are defined by the spacing between the bearings 21 and64 and between the bearing 21 and the bearing ball 50.

When the cassette 14 is removed, the voltage drops back to the value U₁,whereupon the control device 44 emits a "cassette removed" statussignal.

Various changes and modifications to the presently preferred embodimentswill be apparent to those skilled in the art. Such changes andmodifications may be made without departing from the spirit and scope ofthe present invention and without diminishing its attendant advantages.Therefore, the appended claims are intended to cover such changes andmodifications.

What is claimed is:
 1. A device for dispensing sheets from a cassettefor containing a stack of said sheets, the device comprising:anextracting device including:a plurality of extracting rollers forcontacting a top sheet of the stack; a tubular floating shaft on whichthe extracting rollers are mounted; a drive shaft extending axiallythrough the tubular floating shaft; a universal joint mounting a centralsection of said tubular floating shaft to said drive shaft, so that thetubular floating shaft is generally radially pivotable but rotationallyfixed relative to said drive shaft; the tubular floating shaft beingguideably disposed within a guide fork to be displaceableperpendicularly to a plane of said top sheet; one end of the drive shaftbeing rotatably mounted in a bearing; an opposite displaceable end ofthe drive shaft being mounted displaceably perpendicularly with respectto said plane; a pressing device for pressing said stack with a pressingforce against the extracting device; a pressing motor for displacing thepressing device against the rear end side of the stack of sheets by apressing motor; a spring biased against the displaceable end of thedrive shaft to determine the pressing force, the spring having anexcursion displacement which is a measure of the pressing force; adisplacement sensor for measuring the excursion displacement of thespring; wherein the cassette is removable from the sheet-extractingdevice and fittable thereon, the drive shaft having a first displacementposition when the cassette is removed and a second displacement positionwhen the cassette is fitted, the displacement sensor having a measuringrange for detecting an absence or presence of the cassette, and, in thedirection of spring excursion, the sensor having a further measuringrange in which the displacement sensor measures the pressing force ofthe stack of sheets on the extracting device, the sensor emitting asignal to adjust the pressing motor depending the pressing force.
 2. Thedevice as claimed in claim 1, wherein the drive shaft is driven at thebearing-mounted end thereof.
 3. The device as claimed in claim 1,wherein the force of the spring is proportional to the excursiondisplacement over at least part of its excursion.
 4. The device asclaimed in claim 1, wherein the displaceable end of the drive shaft ismounted in a displaceable bearing, and wherein the displacement sensorcomprises a reflection light barrier and a reflector fitted on thedisplaceable bearing having a surface normally oriented in adisplacement direction of the drive shaft.
 5. The device as claimed inclaim 4, wherein the reflector is planar and mirror-surfaced.
 6. Thedevice as claimed in claim 4, wherein the reflector is arranged at adistance from the reflection light barrier such that a spot of lightproduced by the light transmitter is imaged with high definition on thelight receiver and with dimensions which correspond approximately to thelight-sensitive surface area of the light receiver.
 7. The device asclaimed in claim 5, wherein displacement of the reflector causes adisplacement-dependent change in a degree of illumination of the lightreceiver and thus in the output voltage thereof.
 8. A sheet-extractingapparatus with a cassette for receiving a stack of sheets, saidsheet-extracting device comprising:an extracting apparatus having atleast two extracting rollers for abutting against a top sheet which isto be extracted; a pressing device that can press a front end side ofsaid stack, with a pressing force against said extracting device; aguide fork having a plurality of legs, said legs directedperpendicularly with respect to a plane of said sheets; a drive shafthaving a first end rotatably mounted in a frame-mounted bearing and adisplaceable end opposite the first end of said drive shaft displaceablymounted perpendicularly with respect to said plane; a universal joint; atubular floating shaft having a central section, said tubular floatingshaft connected to said drive shaft in a rotationally fixed manner; saidrollers of said extracting device being arranged axially spaced from oneanother on said tubular floating shaft, the central section of saidtubular floating shaft mounted with radial play on said drive shaft viasaid universal joint means, said drive shaft passing through saidtubular floating shaft in a longitudinal direction, said tubularfloating shaft adjustably guided between said plurality of legs of saidguide fork; a pressing motor that can displace said pressing deviceagainst the rear end of said stack; a spring which acts on saiddisplaceable end of said drive shaft, said pressing force determined bysaid spring, said spring having an excursion displacement which is ameasure of said pressing force; a displacement sensor for measuring saidexcursion displacement of said spring, said sensor located near thedisplaceable end of said drive shaft; and said cassette removable fromsaid sheet-extracting device and fittable thereon, said drive shaftassuming a first displacement position when said cassette has beenremoved and a second displacement position when said cassette has beenfitted to said sheet-extracting device, said displacement sensor havinga measuring range, said measuring range determining an absence or apresence of said cassette, and in the direction of increasing excursionof said spring, said measuring range is adjoined by a further measuringrange through which said displacement sensor measures said pressingforce of said stack of sheets on said extracting device and emits asignal for readjusting said pressing motor, dependent on said pressingforce.
 9. The apparatus as claimed in claim 8, wherein a torque isintroduced into said drive shaft at said first end thereof.
 10. Theapparatus as claimed in claim 8, wherein said pressing force determinedby said spring is proportional to said excursion displacement at leastover part of said excursion displacement of said spring.
 11. Theapparatus as claimed in claim 8, wherein said displaceable end of saiddrive shaft is mounted in a displaceable bearing, and wherein saiddisplacement sensor comprises a reflection light barrier and areflector, said reflector fitted on said displaceable bearing and havinga surface normally oriented in a displacement direction of said driveshaft.
 12. The apparatus as claimed in claim 11, wherein said reflectoris planar and mirror-surfaced.
 13. The apparatus as claimed in claim 11,wherein said reflector is arranged at a distance from said reflectionlight barrier such that a spot of light produced by a light transmitteris imaged with high definition on a light receiver and with dimensionswhich correspond approximately to a light-sensitive surface area of saidlight receiver.
 14. The apparatus as claimed in claim 13, wherein thedisplacement of said reflector causes a displacement-dependent change ina degree of illumination of said light receiver and thus in an outputvoltage thereof.